During the construction, maintenance and repair of oil and gas wells it is often desirable to be able to isolate one part of a wellbore from another. This is typically achieved by using a device known as a packer.
Typically, packers are manoeuvred into place at the position where it is desired to create a seal and then inflated.
One of the limitations of existing packers is that they must have an uninflated diameter which is close to the inflated diameter. If this is not the case then the seals may fail particularly if the packers are being used to isolate a section of tubing for pressure testing.
In practice it is often desirable to be able to introduce a packer through a tubular of relatively narrow diameter yet use the packer to seal a tubular of somewhat wider diameter.
At the present time there are no satisfactory solutions to this problem.
The present invention addresses some of the problems involved.
According to one aspect of the present invention there is provided a packer which comprises an elastomeric member which, in use, will deform radially when subject to axial pressure, characterised by a plurality of fingers which are secured to said elastomeric member.
By securing the fingers to the elastomeric material the fingers will contract after radial pressure ceases to be applied to said elastomeric member, and said elastomeric member resumes its original shape. This helps ensure that the packer can be withdrawn through the tubular after use.
Preferably, the fingers will be made of metal, for example, steel. Aluminium and softer metals could conceivably also be used according to the intended duty of the packer.
Advantageously, the elastomeric material is rubber and said fingers are vulcanised to said elastomeric material.
According to another aspect of the invention there is provided a packer comprising an elastomeric material which, in use, will deform radially when subject to axial pressure, characterised by a plurality of fingers which are supported by said elastomeric material and one end of which is retained by a retainer so that when axial pressure is applied to said elastomeric material said fingers pivot outwardly about said one end.
Preferably, said retainer comprises a ring having a recess shaped to receive said one end of said fingers.
Advantageously, said one end of said fingers is rounded.
According to a third aspect of the present invention there is provided a packer comprising an elastomeric material which, in use, will deform radially when subject to axial pressure, characterised by a plurality of fingers which extend circumjacent said elastomeric material and which have cross-sections which co-operate with one another to completely circumscribe said elastomeric material as said elastomeric material is deformed radially when being subjected to axial pressure.
Preferably, alternate ones of said fingers are of wedge shape cross-section facing radially inwardly interdigitated by fingers of wedge shape cross-section facing radially outwardly.
Advantageously, when said elastomeric material is not subject to axial pressure, said fingers project radially outwardly by differing distances. In such embodiments it is intended that when the packer is inflated the radially outer and radially inner extremities of the fingers will lie on substantially concentric circles.
When combined together the above features provide a very desirable packer.
Preferably, the fingers are tapered.
Advantageously, the fingers only extend along part (preferably about one half) of the axial length of the elastomeric member in its non-compressed state.
Preferably, the free extremity of each of the fingers is rounded. This helps to ensure that the fingers do not damage the elastomeric material or the wall of the casing.
Packers in accordance with the present invention may be actuated hydraulically, pneumatically, mechanically or electrically as desired.